1. Field of the Invention
The present invention relates to an apparatus and method for improving transmission efficiency by reducing an influence of other-cell interference in such a manner that a frame region for duty cycle reduction in a conventional transmission frame region is partially allocated to a user by incorporating Zero Forcing (ZF) beamforming.
2. Description of the Related Art
A resource reuse scheme for dividing a system frequency band in a frequency domain or a time domain has conventionally been deployed to reduce inter-cell interference. In this scheme, resource allocation is achieved such that a resource used in each cell (or sector) is different from that used in its neighbor cell.
FIG. 1A illustrates a case where a conventional frequency reuse scheme is used when a reuse factor N is 1. As shown, a Base Station (BS) is located in a center of each cell where data transmission is achieved using the same frequency band.
FIG. 1B illustrates a case where the conventional frequency reuse scheme is used when the reuse factor N is 3. As shown, a BS is located in a center of each cell. By dividing the system frequency band into 3 bands, all BSs can be prevented from using the same frequency resource used in neighbor cells, thereby reducing interference.
The frequency (or time) reuse scheme allows the neighbor cells to use different resources. Thus, there is an advantage in that inter-cell interference can be reduced.
However, an increase in the reuse factor N results in a decrease in a cell throughput which leads to a decrease in a performance gain. This is because a system frequency bandwidth is limited, and an increase in the frequency reuse factor N results in a decrease in an amount of frequency resources that can be used in each cell. Further, since a required transmission amount varies from one user to another, resources may be insufficient or wasted. Therefore, when the frequency reuse factor N is 1, the system operates in a most ideal manner in terms of overall system efficiency, and a highest cell transmission throughput can be determined. However, since all cells use the same frequency-band resource in this case, there is a problem in that reception performance significantly deteriorates when a user is located in a cell boundary.